A recent study has shown the reproducibility of time to exhaustion (time limit: tlim) at the lowest velocity that elicits the maximal oxygen consumption (vVO2 max). The same study found an inverse relationship between this time to exhaustion at vVO2 max and vVO2 max among 38 élite long-distance runners (Billat et al. 1994b). The purpose of the present study was to compare the time to exhaustion at the power output (or velocity) at VO2 max for different values of VO2 max, depending on the type of exercise and not only on the aerobic capacity. The time of exhaustion at vVO2 max (tlim) has been measured among 41 élite (national level) sportsmen: 9 cyclists, 9 kayak paddlers, 9 swimmers and 14 runners using specific ergometers. Velocity or power at VO2 max (vVO2 max) was determined by continuous incremental testing. This protocol had steps of 2 min and increments of 50 W, 30 W, 0.05 m s-1 and 2 km-1 for cyclists, kayak paddlers, swimmers and runners, respectively. One week later, tlim was determined under the same conditions. After a warm-up of 10 min at 60% of their vVO2 max, subjects were concluded (in less than 45 s) to their vVO2 max and then had to sustain it as long as possible until exhaustion. Mean values of vVO2 max and tlim were respectively equal to 419 +/- 49 W (tlim = 222 +/- 91 s), 239 +/- 56 W (tlim = 376 +/- 134 s), 1.46 +/- 0.09 m s-1 (tlim = 287 +/- 160 s) and 22.4 +/- 0.8 km h-1 (tlim = 321 +/- 84 s), for cyclists, kayak paddlers, swimmers and runners. Time to exhaustion at vVO2 max was only significantly different between cycling and kayaking (ANOVA test, p < 0.05). Otherwise, VO2 max (expressed in ml min-1 kg-1) was significantly different between all sports except between cycling and running (p < 0.05). In this study, time to exhaustion at vVO2 max was also inversely related to VO2 max for the entire group of élite sportsmen (r = -0.320, p < 0.05, n = 41). The inverse relationship between VO2 max and tlim at vVO2 max has to be explained, it seems that tlim depends on VO2 max regardless of the type of exercise undertaken.

Using 23 elite male athletes (8 cyclists, 7 kayakists, and 8 swimmers), the contribution of the anaerobic energy system to the time to exhaustion (t(lim)) at the minimal exercise intensity (speed or power) at which maximal oxygen uptake (VO2max) occurs (IVO2max) was assessed by analysing the relationship between the t(lim) and the accumulated oxygen deficit (AOD). After 10-min warming up at 60% of VO2max, the exercise intensity was increased so that each subject reached his IVO2max in 30 s and then continued at that level until he was exhausted. Pre-tests included a continuous incremental test with 2 min steps for determining the IVO2max and a series of 5-min submaximal intensities to collect the data that would allow the estimation of the energy expenditure at IVO2max. The AOD for the t(lim) exercise was calculated as the difference between the above estimation and the accumulated oxygen uptake. The mean percentage value of energy expenditure covered by anaerobic metabolism was 15.2 [(SD 6)%, range 8.9-24.1] with significant differences between swimmers and kayakists (16.8% vs 11.5%, P < or = 0.05) and cyclists and kayakists (16.4% vs 11.5%, P < or = 0.05). Absolute AOD values ranged from 26.4 ml.kg-1 to 83.6 ml.kg-1 with a mean value of 45.9 (SD 18) ml.kg-1. Considering all the subjects, the t(lim) was found to have a positive and significant correlation with AOD (r = 0.62, P < or = 0.05), and a negative and significant correlation with VO2max (r = -0.46, P < or = 0.05). The data would suggest that the contribution of anaerobic processes during exercise performed at IVO2max should not be ignored when t(lim) is used as a supplementary parameter to evaluate specific adaptation of athletes.

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AbstractThe aim of the present study was to investigate the serving techniques in male top level volleyball, especially the tactical and spatial behavior of the servers and receiving opponents focusing on the pros and cons of the different serving techniques. An analysis was made of 4552 serves from 28 matches played during the 2008-2009 regular season of the Italian volleyball male Top League. Serving techniques were categorized into Jump Serve (JS), Float Jump Serve (FJS) and Float Serve (FS), and for each serve several parameters were recorded: role of the server (Setter -S, Hitter -H, and Middle Blocker -MB), kind of serve (JS, FJS, FS), number of players defending the serve (Defense), difficulty in receiving the serve (RS), evaluation of serve outcome (EV), and defensive court zone where the ball was directed (FZ). The results confirmed the largest use of the JS (69.9%), followed by the FJS (26.9%) and the FS (3.3%). There were significant relationships between the serve technique, the EV, the Defense and the FZ where the serves were directed (Chi-Square p = 0.000). The zone absolutely most hit was the posterior/central, followed by the left/posteriors. There were significant differences in the RS difficulty for the JS respect to FJS (p = 0.001) and FS (p = 0.000) and also for the defensive strategies performed: a defense strategy with 2 defenders showed significant and better score during the reception respect to that with 3 (p = 0.000). No statistical relationship was found between the role of the server and other parameters. These results are consistent with previous studies in which JS showed to be the most powerful technique in terms of increasing defensive difficulties but, at the sam e time, with a fairly high percentage of errors. This issue must be taken into consideration in crucial phases of the game, and the serving techniques must be used strategically. JS can be very useful for increasing the defensive "conflict zones" with the aim to score a direct ace or to make the offensive maneuver difficult after reception. FJS can be useful when there is the need to aim a specific FZ and prepare the team for the next defense action. Scouting or match analysis procedure of the serving statistics should be performed during the gam e to better indicate the serve strategy to choose. Key words: Match analysis, Notational analysis, Volleyball, Serve technique. Rezumat Rezumat Rezumat RezumatScopul studiului de față a fost investigarea tehnicilor de serviciu la voleibaliștii de top, de sex masculin, în special comportamentul tactic și spațial atât al jucătorilor la serviciu cât și al jucătorilor care realizează preluarea din serviciu, cu focus asupra "pro și contra" în ce Rezultatele confirm ă utilizarea majoritară a serviciului din săritură (JS) -69,9%, urmat de serviciul din săritură planată (FJS) -26,9% și de serviciul planat (FS) -3,3%. S-a găsit o relație semnificativă între tehnica de serviciu, apărare și zona terenului advers în care a fost direcționată mingea (chi-patrat p=0....

Viscous dampers are widely employed for enhancing the seismic performance of structural systems, and their design is often carried out using simplified approaches to account for the uncertainty in the seismic input. This paper introduces a novel and rigorous approach that allows to explicitly consider the variability of the intensity and characteristics of the seismic input in designing the optimal viscous constant and velocity exponent of the dampers based on performance-based criteria. The optimal solution permits controlling the probability of structural failure, while minimizing the damper cost, related to the sum of the damper forces. The solution to the optimization problem is efficiently sought via the constrained optimization by linear approximation (COBYLA) method, while Subset simulation together with auxiliary response method are employed for the performance assessment at each iteration of the optimization process. A 3-storey steel moment-resisting building frame is considered to illustrate the application of the proposed design methodology and to evaluate and compare the performances that can be achieved with different damper nonlinearity levels. Comparisons are also made with the results obtained by applying simplifying approaches, often employed in design practice, as those

In this work, an integrated computational framework for uncertainty quantification and management is presented. Dealing with uncertainty might lead to impractical computational costs especially for detailed models. Hence, it is of paramount importance the availability of efficient numerical methods in order to reduce the computational costs of non-deterministic analyses by implementing the most efficient algorithms and taking advantages of the high performance computing.The computational framework OpenCossan is able to deal with different representation of uncertainty such as random variables, interval, distributional and free p-boxes. A wide range of engineering and scientific problems can be solved by the proposed computational framework thanks to its modular design. An application to a real case multidisciplinary optimization problem involving aleatory and epistemic variables is presented to show the flexibility and the power and the applicability of the software.

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